Lubricating oil composition

ABSTRACT

LUBRICATING OIL COMPOSITION WHICH MAINTAINS A PROPER VISCOSITY AT HIGHER TEMPERATURES AND ALSO A SUFFICIENTLY LOW VISCOSITY SUITABLE FOR GOOD STARTING PROPERTY OF ENGINES, AT LOW TEMPERATURES, CAN BE OBTAINE BY BLENDING A COMPLEX-ESTER OR COMPLEX-ESTERS OF 3-HYDROXY-2,2DIMETHYLPROPYL 2,2-DIMETHYLHYDRACRYLATE (WHICH CAN BE ALSO CALLED HYDROXYPIVALYL HYDROXPRIVALATE) WITH ONE OR MORE KINDS OF STRAIGHT OR BRANCHED CHAIN SATURATED FATTY ACIDS HAVING 4-18 CARBON ATOMS, WITH A SOLVENTREFINED PETROLEUM LUBRICATING OIL.

United States Patent 3,759,862 LUBRICATING OIL COMPOSITION Yukimasa Fukui, 4-3 Umaokoshi l-chome; Tsunehiro Kotani, 30-3 Maedacho; and Toshitsugu Ozeki, 2273-1 Ikuwacho, all of Yokkaichishi, Japan No Drawing. Filed May 16, 1972, Ser. No. 253,728 Claims priority, application Japan, Sept. 30, 1971, 46/76,645 Int. Cl. Cm 1/26 US. Cl. 252-32.7 E 7 Claims ABSTRACT OF THE DISCLOSURE DESCRIPTION OF THE INVENTION This invention relates to lubricating oil compositions obtained by blending a synthetic lubricating oil of a fatty acid ester type with a petroleum lubricating oil and if necessary, further such additives as those which impart antioxidant property, wear resistance and detergency to the resulting blend. The above-mentioned synthetic lubricating oil of a saturated fatty acid ester type is a complex-ester of 3-hydroxy-2,2-dimethylpropyl 2,2- dimethylhydracrylate (which is also called as hydroxy pivalyl hydroxypivalate and will be herein abbreviated as HPHP) with a saturated fatty acid or acids.

It is an object of the present invention to provide a lubricating oil composition which shows improvement in viscosity-temperature characteristic, reduction in evaporation loss, less deterioration, maintenance of detergency or cleanness of engine parts and prevention of wear when used in a gasoline engine for cars or as well as a crank-case oil for diesel engines. It is another object of the present invention to provide a composition effective for various lubricating oil materials which require similar properties such as hydraulic oil, and the like.

With the increase of the importance of highway trafiic, there is a tendency that engines for cars are operated under severe conditions such as heavy load running, long time high speed running, etc. and improvement in performance is continuously being seeked for. At the same time, wear-resistance, thermal and oxidation-stabilities and good detergent and dispersing properties are also required for lubricating oil. Further since there is in driving, a requirement for stability of viscosity of lubricating oil at a higher as well as lower temperature, a multi-grade engine oil which is effective in all seasons has now been produced.

In order to satisfy these many requirements under various conditions at the time of use, for various usages, various procedures to be taken for supplying products of desired properties, such as selection of kind of crude 3,759,862 Patented Sept. 18, 1973 oil, selection of distillation range, solvent dewaxing process, solvent extraction process, hydrofinishing and hydrotreating processes, treatment with sulfuric acid and clay, etc., have been employed in the production of petroleum lubricating oil. Further, in order to impart to these base stocks of petroleum lubricating oil, wear-resistance, thermal and oxidation-stabilities and detergent and dispersing properties, various kinds of additives are added, but the properties of products are not always satisfactory in all respects when the object of use is varied.

When motor oils having various 'SAE (Society of Automotive Engineers) viscosity numbers such as multi-grade engine oil SAE l0W-30, 1OW-40, 10W-50, or 5W-30 are to be prepared, it has heretofore been attempted to add a viscosity index improver of a high molecular weight material such as polyisobutene, polymethacrylate, etc. to a base stock of petroleum lubricating oil in order to maintain a proper viscosity at a high temperature and a viscosity sufliciently low to improve the starting property of engines even at a low temperature of 0 F. or lower. However, for the simultaneous fulfilment of both requirements of the starting property at a low temperature and the viscosity characteristic at a high temperature, it is necessary to make the viscosity of a base stock for lubricating oil as low as possible and also add a large amount of a viscosity index improver. However, the addition of a high molecular weight viscosity index improver reduces the shear stability of the lubricating oil and often brings about a sudden drop of viscosity in the initial stage of running.

According to the present invention, it has been found that the addition of a synthetic lubricating oil of saturated fatty acid ester class such as HPHP ester to a petroleum lubricating oil makes up the defects and extends the advantages of the performance originally possessed by the petroleum lubricating oil. This is extremely preferable result at the time of actual use.

The HPHP ester used in the present invention is a complex-ester or complex-esters between one or more kinds of straight or branched saturated fatty acids having 4 to 10 carbon atoms and a divalent alcohol, HPHP. The HPHP ester includes those in which the same kind of the acid is reacted with HPHP, those in which different kinds of the acid are reacted with HPHP, and mixtures thereof.

The chemical structural formula of the HPHP ester is indicated in the following way:

(I) Hydroxypivalyl hydroxpivalate: molecular weight,

204; RR, 92.8 C. (0.2 mm. Hg)

(II) Saturated fatty acid: R and R are the same kind or different kinds of alkyl groups of C -C,

(III) HPHP ester:

Properties of HPHP esters prepared from various kinds of aliphatic monocarboxylic acids are shown in Table 1.

TABLE 1 General properties of HPHP ester synthetic lubricant CH f/Hs R $--O-CHg- CHzO-C(|]CH:O%R

C H; O CH;

R; and R are same or different Alkyl part of saturated fatty Kinematic viscosity acids used in the Specific Flash Pour (cst.) at- Synthetic preparation of gravity, point, point, Viscosity lubricant HPHP ester 15/4 0. 0. C. 37.78 C. 98.89 0. index HPHP-4.-. Il-OaH1 1.010 190 60 9. 62 2. 38 63 HPHP-6". n-CsHu 0.988 194 -60 12.59 2. 87 77 HPHP-8.... n-C1H1s 0.959 238 60 14. 29 3.36 120 H PEP-12. n-(igaa (557) 0. 927 268 10 22. 30 4. 80 153 HPHP ss (45%) 953 234 60 16.70 3.75 125 v n HPHP31 n-OnHzs (75%) 0 938 260 -17.5 25.10 5.05 144 -CraHzz o) -Cu n (7% media HPHP-71.- (17%) 0. 964 224 -60 16. 34 3.60 112 -CsHu a w i-Cti-Cu The HPHP ester useful in the lubricant composition of the present invention has three ester bonds in a molecule as shown above and the following characteristic properties:

This ester has a low volatility, a high flash point and a low pour point. Its viscosity-temperature characteristic is excellent as in other diester synthetic lubricating oils such as sebacate esters and adipate esters, and viscosity index increases with the increase of carbon atoms of the saturated fatty acid component of HPHP ester. Further, since the fl-carbon atom of the alcohol component of HPHP ester is not combined with hydrogen, the thermal stability of HPHP ester is exceedingly high. By the comparison with synthetic lubricating oils of diester class or compound esters with polyols such as neopentyl glycol and trimethylol propane, it has been found that HPHP ester has superior thermal stability.

When the HPHP ester having so many characteristic properties is added to a base stock of petroleum lubricating oil in an amount of 595% by volume, preferably 10-50% by volume, it is easy to formulate a multi-grade engine oil prescribed in the SAE viscosity classification, and it is possible to overcome various drawbacks of engine Oils which have not been heretofore solved.

When various kinds of multi-grade engine oils according to the SAE viscosity classification are formulated by mixing a petroleum lubricating oil, HPHP ester, a viscosit index improver and other necessary additives, and in case where the formulated oils have the same viscosity, the range of selection of base stock of synthetic lubricating oil is extended by increasing the mixing ratio of the synthetic lubricating oil, and thus, high viscosity base stocks of petroleum lubricating oil can be used. Moreover, at the same time, it is possible to save the amount of the viscosity index improver to be mixed.

The lubricating oil composition having incorporated therein a HPHP ester is superior in thermal stability and wear resistance. It is necessary, as is well-known, to add zinc-type antioxidant such as zinc dialkyldithiophosphate to gasoline or diesel-engine oil in order to impart antiwear property. The HPHP ester used in the present invention, different from other ester-type synthetic lubricating oils, is superior to the additive effect of antioxidant, and hence the lubricating oil composition in which the HPHP ester is incorporated in the base stocks of petroleum lubricating oil showed also superior results.

The experimental results carried out according to the 115 K-2514 testing method of oxidation stability for internal combustion engines, showed that the lubricating oil compositions of the present invention have total acid value and viscosity increase, both repressed at a low value, respectively, are extremely good in lacquer rating and superior in detergency.

Also in the experimental results carried out according to I15 K-2540 of thermal stability testing method for turbine oils, the lubricating oil compositions of the present invention showed total acid value and viscosity increase, both repressed at a low value, respectively, and low evaporation loss, as compared with petroleum lubricating oils. Also, with regard to sludge deposition which is often encountered in the long time test of petroleum lubricating oils (72 hours, C.), there was no sludge deposition in case of the oil having incorporated therein HPHP ester. Accordingly, it can be pointed out here also that the incorporation of HPHP ester into a petroleum lubricating oil according to the present invention, brings about the advantage in the saving of the amount of a detergent, dispersing agent to be added.

In the present invention, various kinds of viscosity index improvers such as polyalkyl methacrylates having as the alkyl, e.g. C -C polyalkyl methacrylates having detergent and dispersing properties in addition to viscosity index improving property, e.g. copolymers of alkyl methacrylate having as the alkyl, e.g. C -C with diethylaminoethyl methacrylate, polybutene, etc., can be added to the lubricating oil composition of a solvent-purified petroleum lubricating oil and HPHP ester or esters.

The amount of the improvers to be added is preferably in the range of 120% by volume based on the volume of the lubricating oil composition.

Further, various kinds of antioxidants such as zinc dialkyl dithiophosphates, e.g. zinc di-n-butyl-dithiophosphate, phenolic compounds, e.g. bisphenol, etc. can be added to the lubricating oil composition. The amount of the antioxidants to be added is preferably in the range of 0.02-2% by volume based on the volume of the lubricating oil composition.

Furthermore, various kinds of detergent and dispersing agents such as sulfonate compounds, phenate compounds, e.g. over-based Ca or Ba petroleum sulfonate or phenate, non-ash detergent and dispersing agents e.g. succinic imide, the above-mentioned polyalkyl methacrylate having detergent and dispersing properties in addition to viscosity index improving property, can be added to the lubricating oil compositions.

The amount of detergent and dispersing agents to be added, is preferably in the range of 0.l-10% by volume based on the volume of the lubricating oil composition. The superiority of the oil having HPHP ester type synthetic lubricating oil incorporated therein to petroleum lubricating oils will be illustrated by the following examples containing engine tests.

Example 1 By using as base stocks of petroleum lubricating oils, solvent-refined neutral oils --90, 200, 300 and 400, and adding thereto HPHP-85 ester and various additives such as a viscosity improver, a detergent, disperging agent, an antioxidant, etc., multi-grade motor oils were prepared as shown in Table 2. As seen from Table 2, when the viscosities of the formulated oils are same, it is possible to extend the selection range of viscosity of petroleum base stock and to use a higher viscosity base stock by increasing the mixing ratio of the synthetic lubricating oil, and also possible at the same time to reduce the amount of viscosity index improver to be mixed. Control in Table 2 shows the case of conventional lubricating oil in which no HPHP ester was added.

Example 3 Lubricating oil compositions obtained by mixing HPHP esters with a solvent-refined base stock of petroleum lubricating oil in a fixed mixing ratio were subjected to an oxidation stability test according to the testing method of HS K-2514 at a testing temperature of l65.5 C. for 48 hours by using well-polished iron pieces and copper pieces. 250 m1. of each oil to be tested was charged in a test vessel which was then immersed in an oil bath maintained at a fixed temperature. Stirring glass rod was inserted into the test vessel and the oil to be tested was stirred at a high revolving speed of 1300 rpm.

TABLE 2 Example of multi-grade motor oil formulated Example ll 1-2 l-3 14 1-5 1-6 Control Classification oi SAE viscosity 10W-30 10W-30 10W-40 low-40 10W-50 10W-50 10W-5O Lubricating oil composition (vol. percent):

Neutral oil cst 8 30 (6. 7) 65. (9. 1) 80.0 (6.2) 62. 3 (7. 8) 74. (5. 7) 60. 0 (7.0) 82. 3 (5. 2) HPHP-85 9. 1 27. 3 8. 7 26. 7 8.5 24. 0 Polymethacrylate 2 5. 4 3. 2 7. 7 7. 2 11.0 10. 0 11. 7 Over-based Ca petroleum sulfonate- 3. 5 3. 5 3. 4 3. 6 5.0 5.0 5. 0 Zinc di-n-butyl-dithiophosphate 1.0 1.0 0.2 0.2 1. 0 1. 0 1. 0 Properties of lubricating oil:

SIpecific gravity (/4 C.) U. 893 0.890 0. 884 0.898 0.880 0.891 0. 884

iscosity:

100 F. (0st.) 80.0 66. 4 84. 0 80. 5 110. 5 108. 5 107. 4 210 F. (est)- 11. 1 9. 85 13. 9 13. 1 17. 8 17. 0 l7. 8 F. (cp.) 2, 080 2, 400 2, 400 2, 200 2, 350 2, 300 2, 300 Viscosity index. 138 142 182 174 189 182 193 Pour point C.) -30 -30 -32. 5 30 -32. 5 32. 5

1 Solvent-refined oil, values in brackets show viscosities at 210 F.

2 Viscoplex, a trademark of product prepared by Rolim & Haas Co. Ltd. which is a copolymer of polydiethylaminoethyl methacrylate (20%) and polyalkyl methacrylate (80%) (alkyl: CL'ClK).

I Observed values of viscosity by means of Gold cranking Simulator.

EXAMPLE 2 Thermal stability test according to 11$ K-2540 Was carried out for lubricating oil compositions in which a solvent-refined neutral oil-200 was used as a base stock of lubricating oil and HPHP ester was incorporated therein. The result of the test is shown in Table 3. Compared with a petroleum lubricating oil alone, there was no deposit of sludge observed, the increase of total acid value was repressed at a low value and products showed a good thermal stability.

TABLE 3 Thermal stability test oi lubricating oil composition [According to J IS K-2540 (170 C. 72 hr.)]

Increase of total acid viscosity Lubricating oil composition Dlsooloratlon number (mg. ratio, Evaporation (vol. percent) grade Sludge KOH/g. 100 F. loss, percent Example 2-1 .-{g%% h 8 C None. 2. 6 5. 2 23.5 Example 2-2 ngiP f filg o .-do.- 1. 5 4.4 19.1 Example 2-3 ngg gglgi gggg (70)} o do- 1.3 a. 2 16.0 Example 24 ..{}1" o .-do 1. 9 4.7 28.8

2. 9 21. 5 2. 4 1. 6 14. 6o HPHP-31 2. 1 1. 4 8. 4 HPHP-8 (100) 2. 9 1. 6 20. 7 Control 2-5 IlqDi (t2I-eth3i7llh2%1(r)y(l%0s)ebacate (100 21.2 2. 5 24. 6

en a o {Di (2-ethylhexyl) sebacate (so) 6 4 0 l Precipitated in a large amount. I Unmeasurable.

TABLE 4 Thermal stability test of lubricating oil composition According to MS K-2514 (l65.5 (1X48 hr.)]

Increase of Viscosity total acid ratio, number, mg. Lacquer Lubricating oil composition (vol. percent) 100 F. KOH/g. rating Neutral oil-200 (69.85) Example 3-1 HPHP-85 (29.90) 1.06 0.6 None.

Zinc di-n-butyl-dithiophosphate (0.25)- Neutral oil-200 (69.85) Example 3-2 HPHP-85 (29.90) 1.18 2. 2 Do.

Bisphenol (0.25) Neutral oil-200 (6985).. Example 3-3 HPHP-31 (29.90) 1. 05 0. 40 Do:

Zine di-n-butyl-dithiop Neutral oil-200 (69.85). Example 3-4 HPHP-71 (29.90) 1.07 0.5 Do.

ginctdlin-iliugoyal-githigphosphate (0.25)

cu m o 9.75 (3mm! "lfirgfilli-rggpgglggithiophosphate (0.25 07 90 Contml l d ;.t1 1a%i5st5%sg.%' zaiieji'jiij} 02 58 -e y exy se acate 9 {Zinc di-n-butyl-dithiophosphate 0.25

Example 4 positions prepared by mixing solvent-refined neutral oils A solvent-refined neutral oil 200 and a HPHP ester were mixed in a volume ratio of 70 to 30. The mixture was subjected to a panel coking test according to Federal Test Method Std. No. 79la-3462.

As for testing conditions, a panel temperature of 250 C., a temperature of oil reservoir of 100 C., an oil splashing interval of 1.5 seconds operation followed by stop of 13.5 seconds, and a test duration time of 5 hours were employed. By measuring the resulted amount of coke formed on the surface of aluminum panel, detergency of oil was evaluated. The results of this test are shown in Table 5.

The test results for the single uses of petroleum lubricating oil and of synthetic lubricating oil are indicated in Table 5 as controls.

According to these results, the lubricating oil in which synthetic lubricating oil was mixed, showed less coke formation and superior detergency as compared with the petroleum lubricating oil alone.

Among synthetic lubricating oils, a compound ester such as HPHP ester showed better result than a diester such as sebacate.

with HPHP ester type synthetic lubricating oils, and evaluation was carried out with regard to changes of properties of used oils, bearing abrasion corrosion ten- 30 dency and cleanliness of piston. Their results are shown in Table 6.

As controls, the experimental results for both the cases of a petroleum lubricating oil, alone, and a lubricating oil composition in which another ester was incorporated are shown in Table 6. According to these results, the lubricating oil compositions containing HPHP ester type synthetic lubricating oil incorporated showed superior wear resistance and detergency, as compared with both the cases of the petroleum lubricating oil, alone, and the 0 lubricating oil composition in which another ester was incorporated.

The testing conditions were as follows:

Petter-W1 engine: water cooled single cylinder 4 stroke engine,

Cylinder inner diameter: mm., Stroke: 82.5 mm., Piston displacement: 470 ml., Compression ratio: 5:1, Operation time: 36 hr., Engine revolution: 1500 r.p.m., Output: 3.3 H.P., Air, fuel ratio: 11.7-12.1,

TAB LE 6 Panel coking test of lubricating oil composition Example Control Lubrleatin oil composition (vol. percent):

Neutra l oil-200 69. 75 70 70 70 92 0 Synthetic lubricating 01L 1 30 l 30 2 30 3 30 1 4 100 Polymethacrylate 5 10 7. 0 Zinc di-n-butyl-dithiophosphate 0.25 1.0 Amount of coke deposit (mg) 4. 2 3. 9 3. 2 3.0 6.0 1. 6 18. 7 Evaluation of cleanliness (10=clean) 9. 3 9. 0 9. 6 9. 7 8. 8 9. 8 9. 2

l HPHP-85. 2 HPHP-31. 3 HPHP-71 4 DOS (di (-diethylhexyl)sebacate. Same with the polymethacrylate in Table 2.

Example 5 Fuel consumption: 113 sec/50 ml., Cooling temperature: C., Oil temperature:

inlet 146 outlet 150 75 Hot spot heater temperature: 200 C.

TABLE Gasoline engine test (Fetter-W-l) Example Control Lubricating oil composition (vol. percent):

Neutral oil-200 83 0g 69. 83 69. 83 99. 05 69. 83 .22 29.92 29.22 29.22 29.22 Over-based calcium petroleum sulionate 70 0. 70 0. 70 0.70 0.70 0. 70 Zinc di-n-butybdithiophosphate 0. 25 0. 25 0. 25 0. 25 0. 25 0. 25 0. 25 Lubricating oil properties: Viscosity (cst.):

100 F 28. 90 29. 70 41. 40 35. 60 29. 60 43. 6 25. 80 210 F 5. 5. l8 6. 40 5. 80 5. l2 6. 39 5. 06 Viscosity index- 115 115 114 115 111 105 115 Evaluation:

Increase of viscosity of used 011 (percent)' 100 F -1 +26 +44 +34 +25 +28 +58 +48 210 F +14 +25 +16 +18 +32 +19 Increase of total acid number (mg. K0 H/g +0. 3 +2. 8 +2. 4 +1. 7 +2. 2 +3. 4 +2. 8 Carbon residue (weight. percent) 28 1. 1 1. 1 1. 2 1. 1 1. 3 1. 2 n-Heptane insoluble (weight percent)-.- 13 0. 16 0. 16 0. 15 0. 16 0. 12 0. 26 Engine evaluation:

Bearing metal weight loss (mg.) 17 198 137 53 126 472 229 Compression ring weight loss ORE.) 73 103 97 86 83 85 124 Ifiston skirt cleanliness (clean-:10) 4. 8 9. 3 9. 3 9. 5 9. 5 8. 4 9. 0

1 HPHP-85. 1 HPHP-31. 3 HPHP-71.

What is claimed is:

1. Lubricating oil compositions which comprise lubrieating amounts of a solvent-refined petroleum lubricating oil and a complex-ester or complex-esters of S-hydroxy- 2,2-dimethy1propyl 2,2-dimethylhydracrylate with at least one straight or branched alkanoic monocarboxylic acid having 4-18 carbon atoms.

2.. Lubricating oil compositions according to claim 1, wherein a viscosity index improver is incorporated therein in an amount of 1-20% by volume based on the volume of the lubricating oil compositions.

3. Lubricating oil compositions according to claim 2, wherein said viscosity index improver is selected from the group consisting of polyalkyl methacrylate having as the alkyl, C C copolymers of alkyl methacrylate having as the alkyl, (lg-C with diethylaminoethyl methacrylate, and polybutene.

4. Lubricating oil composition according to claim 1, wherein an antioxidant is incorporated therein in an amount of 0.02-2% by volume based on the volume of the lubricating oil compositions.

5. Lubricating oil compositions according to claim 4, wherein said antioxidant is selected from zinc dialkyl dithiophosphates and bisphenoL l DIDA (diisodecyl adipate).

6. Lubricating oil compositions according to claim 1, wherein a detergent and dispersing agent is incorporated therein in an amount of 01-10% by volume based on the volume of the lubricating oil compositions.

7. Lubricating oil compositions according to claim 6, wherein said detergent and dispersing agent is succinic 1m: e.

References Cited UNITED STATES PATENTS 2,134,736 11/1938 Renter 252-56 R 3,057,911 10/ 1962 Finch 260-484 3,115,519 12/ 1963 Crouse et a1 252-56 S X 3,210,404 10/1965 Durr et al 252-56 S X 3,655,559 4/1972 Holt 252-56 DANIEL E. WYMAN, Primary Examiner W. H. CANNON, Assistant Examiner US. Cl. X.R.

252-56 R, 56 S, 51.5 A; 260-4106, 484

3,759,862 Dated September 18, 1973 Y'ukimasa Fukui et a1.

Patent No.

Inventor-(5) Q It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading 1:0 the printed specification, after line a S, iriser't of 1/2 to Daikyo Oil Company Ltd. and

1/2 to Kyowa Yuka Comp any Ltd. both of Tokyo, Japan.

Sig med and sealed this 27th day of August 1974.

(SEAL) Attest; McCOY M. GIBSON; JR. g C. MARSHALL DANN Attesting Officer Y Commissioner of Patents 

